ECG measurements are a standard form of cardiac measurement for assessing the condition of a patient's heart. Physicians are trained to interpret a standard set of ECG recordings that are normally obtained by connecting ten electrodes to the patient's body and measuring the voltages between various electrodes and combinations of electrodes as a function of time.
While the standard measurements are easily obtained in a medical setting, such measurements pose challenges when a patient is not in such a setting, which is most of the time. A patient with heart problems would benefit both from a clinical and psychological point of view if the patient could measure the standard set of recordings when symptomatic to determine if the recordings had changed since they were last measured. If the recordings were within the expected range, the patient would be reassured and could go about his or her normal activity. If the measurements were outside the expected range, the patient could transmit them to the patient's physician, the physician could interpret the measurements and advise the patient accordingly or, the measurements can be transmitted automatically to a pre-defined medical entity.
A number of systems for making measurements outside of the clinical setting have been proposed. These systems include some form of ECG electrodes that are attached to the patient's body and connected to a local processor carried by the patient. The local processor typically includes a transmitter that relays the measurements from the unit worn by the patient to a physician at a remote location. The relay mechanism can utilize a telephone line, either land or cellular, or some form of dedicated transmitter.
The systems that duplicate the standard measurements require that electrodes be attached to the patient's body. To provide a full 12 lead ECG recording set, electrodes are typically attached to the patient's upper and lower limbs, as well as to a number of locations on the torso. If the patient is in a setting in which the patient has only limited mobility, such a set of attached electrodes may be acceptable; however, if the patient is fully mobile and attending to his or her normal routine outside of a medical environment, temporary or permanent attachment of the electrodes is not usually acceptable and involves a fair amount of discomfort. Furthermore, the electrodes must be removed when the patient bathes. Hence, some arrangement is needed in which the patient or a caregiver places the electrodes on the patient's body at the time an ECG is to be recorded. A system based on the use of adhesively coated electrodes such as those utilized in normal ECG measurements presents problems from a logistical and cost point of view. The individual electrodes are only usable for a small number of measurements before the adhesive fails. Furthermore, the repeated placement and removal of the electrodes can cause patient discomfort, particularly in patients having body hair in the areas to which the electrodes must be attached. In addition, the patient is often incapable of connecting the electrodes to his or her body at all of the required locations.
Hence, a system that can be utilized by the patient without the help of trained personnel would be advantageous. One such system is discussed in the above-identified co-pending patent application. In that system, a handheld device with four electrodes on the surface thereof is used to generate the 12 standard measurements. The four electrodes are used in various combinations to contact the body at locations that the user can easily reach. By making measurements between various electrodes and various contact points, a good approximation to the conventional 12 standard measurements can be obtained. The device is connected to a communication device that can be used to transmit the data to medical personnel.
The size of this and other portable devices still presents challenges. The above-described device is integrated into a cellular telephone or other form of personal data device. However, it would still benefit from a significant reduction in size so that the device would be no more cumbersome to carry than a USB memory module.